Relation With The Right Ascension
The local hour angle (LHA) of an object in the observer's sky can be calculated
- or
where LHAobject is the local hour angle of the object, LST is the local sidereal time, is the object's right ascension, GST is Greenwich sidereal time and is the observer's longitude (positive west from the prime meridian).
Thus, the object's hour angle indicates how much sidereal time has passed since the object was on the local meridian. It is also the angular distance between the object and the meridian, measured in sidereal hours (1h = 15°). For example, if an object has an hour angle of 2.5h, it crossed the local meridian 2.5 sidereal hours ago (i.e., hours measured using sidereal time), and is currently 37.5° west of the meridian. Negative hour angles indicate the time until the next transit across the local meridian. An hour angle of zero means the object is currently on the local meridian.
Read more about this topic: Hour Angle
Famous quotes containing the words relation with and/or relation:
“[Man’s] life consists in a relation with all things: stone, earth, trees, flowers, water, insects, fishes, birds, creatures, sun, rainbow, children, women, other men. But his greatest and final relation is with the sun.”
—D.H. (David Herbert)
“Concord is just as idiotic as ever in relation to the spirits and their knockings. Most people here believe in a spiritual world ... in spirits which the very bullfrogs in our meadows would blackball. Their evil genius is seeing how low it can degrade them. The hooting of owls, the croaking of frogs, is celestial wisdom in comparison.”
—Henry David Thoreau (1817–1862)